Shuttle astronauts work on station gyroscope

Houston, Aug 1 | Updated: Aug 2 2005, 05:30am hrs
Two spacewalking astronauts, one of them perched on a 50-foot (15-metre) robot arm, worked to replace a failed gyroscope on the International Space Station on Monday, while NASA pondered whether shuttle Discoverys heat shield needs an unprecedented repair.

Japans Soichi Noguchi wrestled to pull the 660-pound (300 kg) gyroscope from the station, then held on while Wendy Lawrence, inside the spacecraft, worked controls to swing the robot arm on which he stood back to Discovery. Youve got a ticket to ride, fellow spacewalker Steve Robinson joked. They were to replace the broken gyroscope, which has not worked since June 2002, with a new one in a 6 1/2 hour spacewalk, the second of at least three they will perform.

NASA said on Sunday a fourth spacewalk might be needed to trim or remove loose material sticking out from heat-resistant tiles on Discoverys belly, an operation astronauts have never done before. The gyroscope replacement is one of the critical tasks of this mission because gyroscopes keep the 200-ton space station correctly positioned. It has four of the units, which look like large toy tops, but only two were working before Discoverys arrival. Robinson and Noguchi repaired the other malfunctioning gyroscope in their first spacewalk on Saturday.